Hydrocarbon cracking process



NOV 7g .1933- F. H. EDsoN. 3199349949 HYDROCARBON CRACKING PROCSS Filed April 29, 1951 KQN 31a/vanto@ ggg l www@ UNITED STATESV PATENT OFI-'Ice HYDl-EOCARBON CRACKIN PROCESS Frank ll. Edson, Westfield, N. J., assigner to I Standard Oil Development Company, a corpof ration of Delaware Application April 29, 1931. Serial No. 533,608

2 Claims. (Cl. -196-51) This invention relates to improvements in 19 respectively. The fractions are passed through the cracking of hydrocarbon oils. pumps 29 and 30 respectively tol independent The invention will bev fully understood from heating coils 31 and 32 disposed in the furnace the following description taken in connection 6, or if desired disposed in separate furnaces 5 with the accompanying drawing in which the fig- The furnace is heated by burners 33 and the 60 ure is a diagrammatic side elevational view partly coil 31 is disposed in the hottest portion of the in vertical section illustrating an apparatus for furnace. The fractions are delivered from coils carrying out the invention. 31- and 32 through lines 34 and 35 respectively,

Referring particularly` to the drawing, referto soaking drum 10. Line 34 opens into the pori ence numeral 1 designates a charging stock line tion of soakingl drum 10 which is most remote 65 through which fresh feed oil is introduced into from discharge line l1, whereas line 35 opens into a lower or intermediate portion of a bubble tower the soaking drum intermediate line 34 and line 9. 2. The fresh feed stock, such as gas oil, mingles The condensate formed'in heat exchangers 18 with thevapors or bottoms in the bubble tower and 19 is conducted by a line 36 to an accumuand is preheated thereby. The. thus treated feed lator 37. It is delivered from accumulator 3 7 70 stock is withdrawn from the bottoml of the bub'v 'through line 38 and pump 39 to a heating coil ble tower through a line 3 in which is. disposedv 40 disposed in the coolest portion of the furnace, apump 4. The pump forces the charging stock and from lthe furnace is delivered through line A through the line 3 into heating coil 5 in the fur- 4l to a portion of the soaking drum 10 intermenace 6 where the charging stock is heated prefdiate'line 9 and the discharge line 11. 75 erably at the' optimum temperatures and pres- It will be clear from the foregoing description sures to effect cracking ofthe oil. 'Ihe heated that in the preferred embodiment each fraction' oil is discharged through line 9 into an intermedias well as the charging stock is independently subate portion of a soaking drum 10. The inlet of jected to that temperature and pressure at which the line 9 into the soaking drum 10 is so positioned the most efficient cracking will occur. The 80 with respect to discharge linev 11 leading from the lighter fractions withdrawn from the uppervp'orsoaking drum that the oil will be digested in the tion of the bubble tower are subjected to the highsoaking drum for a suitable length of time 'to est temperature. The heavier fractions collected secure an optimum cracking time for the oil. in an intermediate portion of the bubble tower Discharge linell is provided with a pressure are subjected to alower temperature. The fresh 85 valve 12 and opens into a separator 15. The feed stock'together with theresidues of the bubblev pressure upon the oil iiowing into the separator 'tower are subjected to a still lower temperature j is reduced and the major portion of the oil vaand the condensate obtained in heat exchangers DOriZeS and Passes upwardly through the Separa-v Y l8-and 19 is subjectedlto still lower temperatures.

35 tor. HGBVY residue, `SuCh aS tar, accumulatg The heated fractionsand charging stock after 90v in the .separator is Withdrawn through adisbeing subjected-to cracking temperature in the "Charge line 16 t0 a Suitable Place .0f disposal, heating coils are commingled in the soaking drum not ShOWIL VHDOIS are Withdrawn from the up- Where they are digested under conditions of temper portion of the separator through a line 17 perature and pressure to produce most eilicient 40 Bud are Passed ,successively lhlOugh frondelisers cracking reaction. The lighter fractions have'a 95 18 and 19. The vapors are withdrawn from conlonger distance to travel through the soaking denser 19 through a line 20 and are delivered drum and hence are digested for a longer time. into an intermediate portion of the bubble tower The successively heavier fractions and charging 2.- vBubble tower 2 contains a plurality of spaced stock are digested for successively shorterperiods plates and bell caps according to the usual conof time. As one example of the process, the 109'.'4

struction. The vapors in passing through the charging stock such as intermediate gas ,oil is bubble tower are fractionated and the unconsubjectedin the cracking coil and soaking drum*- densed vapors, such as light naptha, are` with-v to a temperature of 875 F., more or less, under a l drawn through line 2l to a suitable place of dispressure ofone hundred pounds per square inch,-

posal, not shown. moreor'less.I The temperature and pressure may 105 The fractions are collected at spaced intervals be varied in order to obtain optimum. cracking within the bubble tower and are separately withconditions for the particular charging stock. drawn through lines 23 and 24 to accumulators The lighter fractions, such as heavy naphtha and 25 and 26 respectively and thence are Ipassed lighigas oil, are subjected to highertemperatures 55 through lines 27 and 28 to exchangers 18 and such as 935 and 900? F., respectively. The 1'10 heavier fractions such as heavy gas oil are subl jected to/a lesser temperature, such as 850' F., more or less. The more highly heated light naphtha lremains'in the soaking drum the relativelyy longer length of time necessary to secure the required crackingthereof. The light gas oil, lntermediate gas oil and heavy gas oil are digested for successively shorter lengths of time whereby optimum cracking conditions are obtained for each oil.

It will be understood that a multiple circuit furnace can be used as shown or that aseparate furnace can be used for each fraction. Two or more circuits and furnaces can be used as required depending upon the quality of the charging stock. It will be understood that the operating pressure upon the oil within the heating coils and soaking drums may be varied. A separate soaking drum can be used for each circuit or for two or more of the circuits as desired. The size of the soaking drums used can be varied and the pressures upon the oil can be varied within each drum. If soaking drums for each circuit are used of the same size greater pressures are used upon the lighter fractions. 'Alternatively two of the fractions can be introduced into the soaking vdrum at the same place and some of the advantages oi! the invention will be retained. While the outlet of thesoak'ing drum has been illustrated as being` at the bottom of the soaking drum, it will be understood that the outlet can be at the top and the inlets nearer the bottom of the soaking drum. If desired, two soaking drums and two sets of fractionating. equipment with a multiple circuit furnace or separate furnaces operating at differheated oil into an enlarged digesting zone, digest- I claim; 'f

l. The process of` cracking hydrocarbon oil which comprises subjecting the charging oil to' optimum-temperature and pressure for cracking in an elongated narrow heating zone, digesting the heated oil in an enlarged digesting zone to produce efficient cracking, discharging the digested o il into a vapor separating zone and separating the same into liquid and' vapor fractions, separating the vapor into a plurality of condensate fractions-in a fractionating zone, subjecting the separated condensate fractions while isolated from each other and from the charging oil to optimum conditions of temperature under pres,- sure in independent narrow heating zones, discharging the heated fractions into said enlarged digesting-zone in such manner as to digest a lighter fraction for a longer time than a heavier fraction, and discharging the digested fractions into said separating zone.

2. A process of cracking hydrocarbon oil which comprises subjecting the charging' oil in an elongated narrow heating zone to optimum temperature and pressure for cracking, passing the v ing the heated oil therein to produce efficient cracking, discharging the digested oil into 'a separating `zoneand therein separating it into vapor and liquid, separating the vapor Ainto a plurality of -condensate fractions in a fractionating zone, subjecting the separated condensate fractions while isolated from each other and from the charging oil to independent conditions of temperature under pressure regulate'd to produce the Amoet efficient cracking reactiony of said separate' A11() fractions, digesting the heated fractions in an enlarged digesting zone for progressively longer 'lengths of time in the order of their decreasing specific gravity under superatmospheric pressure to produce emcient cracking, then discharging the digested fractions into said separating zone.

' H. EDsoN. 

